So they trap and re-enforce the solar heat stimulating an effect which is popularly known as green house effect. Thus Green house effect is progressive warming up of the earth’s surface due to blanketing effect of manmade C02 in the atmosphere.
Green House Gases:
The major green house gases are C02, CH4, N20, CFCs. S02 and 03 also enhance global warming. Recently trifluoromethyl sulphur pentafluoride SF5 CF3 present at the height of 8 to 32 Kms above the earth’s surface is found to be 18000 to 22000 times more powerful in trapping atmospheric C02.
Relative contribution of green house gases:-
C02 = 50%, CH4 = 19%, CFC= 17%, 03 = 8%, N2Q = 4%, H2Q = 2%
Global Warming Potential:
The potential of a green house gas to cause global warming is expressed by GWP; it is a function of both the infrared asorption characteristics and the lifetime of the gas. CFC > N20 > CH4 > C02
Harmful Impacts of Global Warming
The global mean temperature will rise by 1 to 3.5°C by the next century. Melting of polar ice will lead to increased radiation as frozen ice is a good reflector of incoming solar radiation. With the increase in temperature soil becomes dry and durf and goes easily to the air.
In cold places it causes smog formation, and in hot places dust particles scatter sunlight by decreasing the extent of sunlight received, as a result photosynthesis process is affected. More flooding of tropical water leads to an increase in schistosomias, a chronic parasitic disease.
Increase rainfall in tropical and subtropical regions produce more stagnant water which becomes a homeland for mosquitoes. Wheat yield decreases with increasing temperature.
Increase in temperature will also extend the growing season for most of the crops. It will also extend the time when insect, pests can breed and may make it possible for some species to have another, generation during the year.
There will be shift of animals and human beings towards higher latitudes. This will be a threat to the extinction species, as they wouldn’t be able to adapt themselves to such conditions. Low lying areas of Kolkata and Dhaka will be flooded. Major coastal cities such as New York, London, Amsterdam, Venice, Singapore and Jakarta may be flooded.
All agricultural crops will respond favourably to increasing atmospheric concentration of C02 but exploitation of the minerals from the soil will increase which can make soil barren.